Numerous processes are within the purview of those skilled in the art for forming toners. Emulsion aggregation (EA) is one such method. EA toners are generally formed by aggregating a colorant with a latex polymer formed by emulsion polymerization. For example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety, is directed to a semi-continuous emulsion polymerization process for preparing a latex emulsion by first forming a seed polymer. Other methods of emulsion/aggregation/coalescing for preparing toners are illustrated in U.S. Pat. Nos. 3,644,263; 3,879,327; 4,243,566; 5,403,693; 5,418,108; 5,364,729; 5,346,797; 5,527,658; 5,585,215; 5,650,255; 5,650,256; 5,501,935; 7,683,142; 7,977,024; 8,124,309; 8,163,459; and 8,168,699, the disclosures of which are hereby incorporated by reference in their entirety.
Polyester toners with low melt properties can be prepared using amorphous and crystalline polyester resins. These polyesters must be formulated into emulsions prepared by solvent containing batch processes before they can be incorporated into the toners. The solvent-containing batch processes include, for example, solvent flash emulsification and/or solvent-based phase inversion emulsification (PIE).
Batch processes can be difficult to scale up because their process inputs such as resin acid value, solvent evaporation rate, and neutralization agent evaporation rate could vary and, thus, could cause a wide range in process noises. As a result, a large amount of time and materials could be wasted by taking a trial and error approach, even at laboratory scale, to determine a critical point for preparing a latex with desired particle sizes.
Moreover, conventional PIE processes typically use mechanical agitation, which may not be able to sufficiently and reliably control the mixing efficiency throughout a whole reaction vessel due to the non-Newtonian behavior of liquid-phase materials during the emulsification process. A high mixing field only localizes at the impeller tip, and the mixing strength decreases away from the impeller, especially along the vessel wall region. Also, dead spots or shallow spots with inefficient mixing can be distributed along the edge of the shaft. Further, establishing a more efficient and more complex impeller design might increase cost. Thus, batch-to-batch consistency can be difficult to achieve at this stage.
It would be advantageous to provide a method for preparing a latex or emulsion suitable for use in a toner product, that is more efficient, takes less time, and results in a more consistent toner product than conventional methods for making toner.